Both of these documents should be available at any dealer, as well as many places online. Most often there will be a small fee associated with wiring diagrams.
If a repair shop will not run you off a schematic then go to a parts house and buy a Haynes Manual.
you can buy repair books one is the haynes repair manual#92075.It has wireing diagrams in the back or go to the dealer
Schematic Diagrams are simple diagrams that illustrate the major components and function of a system such as hydraulics or fuel, etc. This is used for training or general reference. Some schematic will have detailed information that will help the mechanic to diagnose a problem or repair it. Engineering drawings provide detail information as to dimensions or material or details. For details of the wiring, the mechanic must use the Wiring Diagram Manual. For details of the installation and test procedure, the Aircraft Maintenance Manual is required. These schematics drawings may be published in a manual called the Schematic Manual. Douglas refers to this as their LAMMs Schematic (but I don't know what that stands for.)
Haynes makes a manual with the wiring schematic for the O2 sensor on a 1991 Chevy Blazer S10. The manual can be found at most book stores.
An additional service manual and wiring schematic for an A1990 Kawasaki ZX6 motorcycle can be found on eBay as well as at specialty motorcycle dealerships.
My Chilton repair manual - engine wiring schematic shows ( 2 ) heated oxygen sensors for the 1993 Ford Explorer
The wiring diagram and schematic are in the installation manual.
you should buy the Haynes repair manual for that year (1975-1979.) It's got wiring diagrams for all the models, manual, auto, a/c, etc... if you crawl around under your dash, you'll find a white tag that's half-electrical taped onto the wiring harness, and that has the part number, so you can match it up with the manual. you could probably find the schematic online, but if you own one of these cars, the Haynes manual is invaluable. and no, I'm not a Haynes salesman.
I got mine from a repair manual purchased at the auto parts store. there are manuals available from ebay. and there are at least two web sites that sell parts for the Grand wagoneer. there may be schematic available on line.
Wiring diagrams for most cars can be found in the do-it-yourself repair section of autozone.com
You can find a wiring schematic for the fuel pump circuit open wiring on a 1991 Town Car in do-it-yourself repair manuals. Haynes makes one of the most popular manuals.
All of you wiring should be listed in the owners manual. Depending on what wiring you are looking for, you should be able to find a diagram.